I love the art and idea! Three pieces of advice:
1) when you get hit, instead of getting hit down I think you should get immunity for half a sec (or get immunity while getting up) because you often get hit once and then are screwed.
2) Having played Sekiro (and all Soulslikes)the parry window needs to be larger if you can't spam the button. it's insanely hard to time right and the fun from those games mostly comes from learning attack patterns, not good timing.
3) I assume the big sword is just for now, but I would love to see range play a part in the boss so that the dash has good use (like you can just retreat from attacks that are really hard if you want but its a trade-off for the poise meter)